The present research proposal continues work on understanding the development of a learned, vocal repertoire in a samll, Australian parrot--the budgerigar (Melosittacus undulatus). We have demonstrated that: (1) at least part of the vocal repertoire of the budgerigar develops through learning, (2) budgerigars are specialized for the perception of these vocal signals, (3) budgerigars have natural perceptual categories for vocal signals, and (4) the boundaries of some of these perceptual categories may be influenced and refined by learning. The budgerigar offers an excellent model for studying the interaction of basic biological factors operating during the ontogeny of a learned vocal communication system. The proposed experiments focus on the role of perceptual processes in the development of learned vocalizations. The experiments in this proposal directly address the issue of whether "special versus "general" perceptual and cognitive abilities are involved in the devlopment and maintenance of this complex vocal communication system. This issue is especially important since it lies at the heart of current controversies concerning the ontogeny of human language. It is precisely because vocal learning in the budgerigar appears to be somewhat different than that described in songbirds yet so rich and complicated that the budgerigar model may offer the possibility of even more penetrating insights into the basic biological foundations of human language. As in the previous proposal, the overall goal of this research remains the same--to understand how the separate elements involved in the ontogeny and maintenance of a vocal communication system conspire to facilitate the learning of vocal signals.